NaN error in Percentage text box

I created a text box, then applied a percentage formula. When I preview the form, the Percentage field shows a NaN error because the fields it is averaging have a default value of $0.00. Once I type numbers into these fields, the NaN error disappears and the percentage amount displays correctly. How can I get rid of the NaN error when I preview the form?

Re: NaN error in Percentage text box

Thank you, Gennady. I changed my fields from Currency formatting to Number formatting, but the form still opens with the NaN error in the Percentage field. Do you know what else might cause the Nan error?